Method for estimating gradient of actual crystalline lens and intraocular lens

Abstract

The invention discloses a method for estimating the gradient of an actual crystalline lens and an artificial lens, which comprises the following steps of: acquiring the gradient of the crystalline lens or the artificial lens in each image through a B scanning image output by a measuring instrument, or exporting the image and measuring the gradient by adopting a three-point circle drawing mode through image processing software when the instrument cannot directly output; extracting a maximum gradient value and a second maximum gradient value; and determining the inclination direction according to the angles of the two, and determining the actual inclination angle direction and position by adopting an interval estimation mode. According to the invention, indirect acquisition of the spatial attitude can be realized on conventional two-dimensional inspection equipment, and the method is suitable for preoperative evaluation and clinical auxiliary judgment in resource-limited areas.

Description

Technical Field

[0001] This invention belongs to the field of ophthalmic imaging, specifically relating to a method for estimating the tilt of an actual lens and an artificial lens. Background Technology

[0002] The IOL Master700, ANTERION, and ZW-30 are all biometric instruments based on the principle of swept-frequency optical coherence tomography (SS-OCT). These instruments scan the eyeball from 0 to 180 degrees in a diopter of 180° / (number of B-scan images) centered on the visual axis or corneal topography axis (see instruction manual). Figure 1 Finally, we can obtain B-scan images of the eyeball in the 0-360° direction at 180° intervals (number of B-scan images).

[0003] These ophthalmic examination devices typically only acquire B-scan images. While some instruments can provide in-plane data on the tilt and eccentricity of the lens or intraocular lens, they cannot output accurate three-dimensional tilt and eccentricity. Devices with 3D modeling capabilities are not yet widespread, mainly concentrated in a few large tertiary hospitals. Most medical institutions use equipment that cannot directly acquire spatial orientation information of the lens or intraocular lens, or only provide partial data, which is insufficient to meet the needs of preoperative assessment and clinical decision-making.

[0004] Therefore, this paper proposes a method for estimating the three-dimensional tilt of actual lenses and artificial lenses. Summary of the Invention

[0005] This invention designs a method for estimating the three-dimensional tilt of actual lenses and artificial lenses to solve the problems existing in the background art.

[0006] To achieve the above-mentioned technical effects, the present invention is implemented through the following technical solution:

[0007] A method for estimating the tilt angle of an actual lens and an artificial lens, characterized by comprising the following steps:

[0008] S1: The tilt angle of the lens or intraocular lens in each B-scan image of each test subject is output by the measuring instrument, or if the instrument cannot directly output the tilt angle, the tilt angle is obtained by exporting each B-scan image and using image processing software to measure it using the three-point circle method.

[0009] S2: Find the maximum and second maximum tilt angle of the test object;

[0010] S3: Determine the direction of each tilt angle based on the angle of the maximum and second largest tilt angles;

[0011] S4: The actual tilt angle is replaced by the maximum tilt angle. The actual tilt direction is located within the first interval, and the first interval is: [the location of the maximum tilt angle - 90° / (number of B-scan images), the location of the maximum tilt angle + 90° / (number of B-scan images)]; the location of the actual tilt angle is the midpoint of the first interval, that is, [the angle of the direction of the maximum tilt angle - 45° / (number of B-scan images), the angle of the direction of the maximum tilt angle + 45° / (number of B-scan images)].

[0012] Furthermore, in S4, the sign is determined by the position of the second largest tilt angle. It is positive when the degree of the direction where the second largest tilt angle is located is greater than the degree of the direction where the largest tilt angle is located, and negative otherwise.

[0013] The beneficial effects of this invention are:

[0014] This invention provides a method for obtaining lens or intraocular lens tilt and eccentricity based on B-scan images. It is applicable to widely used examination devices such as the IOL Master 700, ANTERION, and ZW-30, which only output two-dimensional images. Compared to solutions relying on dedicated three-dimensional modeling equipment, this method can indirectly obtain the spatial orientation parameters of the lens or intraocular lens by analyzing multiple scan images without the need for three-dimensional modeling, exhibiting high measurement accuracy and feasibility. Furthermore, this method overcomes the limitations of existing equipment in terms of limited data dimensions and restricted application, making it particularly suitable for preoperative assessment in resource-constrained areas. Through this method, clinicians can identify lens eccentricity or tilt preoperatively, providing a basis for decision-making regarding the implantation of a functional intraocular lens, thereby reducing the risk of postoperative visual quality decline due to abnormal intraocular lens position and improving patient satisfaction. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of each B-scan image when 6 B-scan images are output in this invention;

[0017] Figure 2 This is a schematic diagram showing the relationship between the lens tilt angle and the scanning axis in a B-scan image of the present invention;

[0018] Figure 3 This is a schematic diagram of the projection of the lens optical axis in different scanning planes in this invention;

[0019] Figure 4 This is a diagram showing the angular relationship between the optical axis of the lens and its projection in this invention;

[0020] Figure 5 This is a B-scan image of a cataract patient in this invention;

[0021] Figure 6 The B-scan image of the intraocular lens in this invention is a line connecting the centers of the circles fitted by parabolic curves on the anterior and posterior surfaces of the intraocular lens.

[0022] Figure 7 This is a graph of the original measurement results exported by third-party software in this invention;

[0023] Figure 8 This is a data diagram with the original data labeled in this invention;

[0024] Figure 9 This is a graph showing the results of measuring the tilt angles in six B-scan images in this invention.

[0025] Figure 10 This is a table of excerpts of measurement results from multiple measurers in this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] See Figures 1 to 10 As shown, a method for estimating the tilt angle of an actual lens and an artificial lens is characterized by comprising the following steps:

[0029] S1: Output the tilt angle of the lens or intraocular lens in each B-scan image of each test subject through a measuring instrument (such as ZW-30, etc.), or if the instrument (such as IOL Master700, ANTERION, etc.) cannot directly output the tilt angle, export each B-scan image and use image processing software, such as ImagePro plus 6.0, to measure it using the three-point circle method.

[0030] S2: Find the maximum and second maximum tilt angle of the test object;

[0031] S3: Determine the direction of each tilt angle based on the angle of the maximum and second largest tilt angles;

[0032] S4: The actual tilt angle is replaced by the maximum tilt angle. The actual tilt direction is located within the first interval, and the first interval is: [the location of the maximum tilt angle - 90° / (number of B-scan images), the location of the maximum tilt angle + 90° / (number of B-scan images)]; the location of the actual tilt angle is the midpoint of the first interval, that is, [the angle of the direction of the maximum tilt angle - 45° / (number of B-scan images), the angle of the direction of the maximum tilt angle + 45° / (number of B-scan images)].

[0033] In S4, the sign is determined by the position of the second largest tilt angle. It is positive when the degree of the direction of the second largest tilt angle is greater than the degree of the direction of the largest tilt angle, and negative otherwise.

[0034] Example 2

[0035] Figure 1 This is a schematic diagram based on 6 B-scan images. Among them, Figure 1 Figure a illustrates the method of scanning the eyeball with the scanning center as the reference, scanning the number of images every 180° / B (30° in this embodiment), and the red line indicates the scanning direction in each plane figure; Figure 1 Figures b through g in the diagram illustrate the scanning direction in each B-scan image, with the blue line representing the direction of the scanning plane in which the image is located.

[0036] Figure 2 This diagram illustrates the relationship between the lens tilt angle and the scanning axis in a B-scan image. While the scanning axis referenced by different instruments varies slightly—some use the optical axis as a reference, others the corneal topography axis—the vertical axis of the scanned image is always the scanning axis. This diagram uses scanned images from 0° to 180° as an example, with the left side representing the 180° direction and the right side representing the 0° direction. The angle between the lens optical axis and the scanning axis is the tilt angle, and the tilt direction shown in the diagram is towards 180°.

[0037] Figure 3 A coordinate system is established with the scanning axis as the Z-axis. There are six scanning planes from 0 to 180°. Plane B is the scanning plane containing 45° / 225°, and plane A is the scanning plane containing 60° / 240°. The blue line L represents the actual optical axis of the lens, with an actual tilt angle of α. l is the projection of this vector onto the XY plane. Lines a and b are the projections of the actual optical axis onto planes A and B, respectively, with angles β and θ between them and the scanning axis. 1 and b 1 Then, these are their respective projections onto the XY plane.

[0038] Figure 4 In the diagram, the optical axis L is projected onto plane A by line a, onto plane B by line b, and their respective projections l and a onto plane XY.1 b 1 A relationship diagram, where ω represents the relationship between l and a. 1 The included angle satisfies ω < 15°.

[0039] Figure 5 and Figure 6 In this set of images, which are B-scan images exported from IOLMaster700 with a scanning direction of 180-0 degrees, all measurements were performed using ImageProplus 6.0. Figure 5 This is a B-scan image of a cataract patient. The horizontal line in the center of the image is the visual axis, while the lens axis is the line connecting the center of the circle fitted by the parabolic curves of the anterior and posterior surfaces of the lens. The angle between the lens axis and the visual axis is the lens tilt angle, and the tilt direction of this tilt angle is 180°. Figure 6 The B-scan image of the intraocular lens shows that the intraocular lens axis is the line connecting the centers of the circles fitted by the parabolic curves of the anterior and posterior surfaces of the intraocular lens. The angle between the intraocular lens axis and the visual axis is the tilt angle of the intraocular lens, and the tilt direction of this tilt angle is also 180°.

[0040] Figure 8 In the diagram, the data after labeling the original data are shown. The data in the red box corresponds one-to-one with the original data. The green box contains the project content to be exported, and the blue box contains the tilt angle. This angle is less than 20 degrees. If the measurement result is "180°+" or "350°+", then it is necessary to subtract 180 degrees and 360 degrees respectively and take the absolute value (see...). Figure 9 The result is the actual tilt angle.

[0041] Figure 9 This is the result of measuring the tilt angle in all 6 B-scan images. The sign of the tilt angle does not represent its magnitude, but only its direction. For example, a negative sign indicates a downward tilt angle, and vice versa. In the figure, the red box shows the tilt angle measured in each of the 6 B-scan images in a sample; the blue box shows the tilt direction of each image's tilt angle; the yellow box shows the tilt direction of the maximum and second-largest tilt angles; and the green box shows the range of the actual tilt angle. The actual tilt angle's tilt direction can be represented by the midpoint of that range.

[0042] also, Figure 9The first image shows the tilt angle intervals: positive: 0°, -180°; the second: positive: 30°, -210°; the third: positive: 60°, -240°; the fourth: positive: 90°, -270°; the fifth: positive: 120°, -300°; and the sixth: positive: 150°, -330°. The sign is determined as before: (if the Y-coordinate of the anterior surface parabola of the lens or intraocular lens is greater than the Y-coordinate of the posterior surface parabola, it is negative; otherwise, it is positive). The first and second largest values ​​are selected. The interval containing the second largest value is the lower limit of the actual tilt angle interval. The upper limit of the interval is 15 degrees higher than this. The actual tilt direction is (lower limit + upper limit) / 2. The maximum tilt angle ≈ the actual tilt angle.

[0043] Figure 10 This is a selection of measurement results from 157 subjects. Except for the content in the red box, all other data can be automatically output by the instrument. All data in the red box were measured using the estimation method of this patent.

[0044] Example 3

[0045] The detailed derivation process of the mathematical principles of this invention is as follows: Figure 3 and Figure 4 As shown in the example (using 6 B-scan images): the blue line L is the actual optical axis of the lens with an actual tilt angle of α, and l is the projection of this vector onto the XY plane; lines a and b are the projections of the actual optical axis onto planes A and B, respectively, with angles β and θ between them and the scanning axis, while a... 1 and b 1 Let |z| be the projections of each vector onto the XY plane, such that |z| equals 1 for all three vectors. Then tan(α) = |l| and tan(β) = |a|. 1 |、tan(θ=|b 1 |, therefore

[0046]

[0047] Similarly,

[0048]

[0049] And |l|, |a 1 |、|b 1 The positional relationship of the three is as follows: Figure 4 As shown, a 1 b 1 Let a and b be the projections of a and b onto the XY plane, respectively, and ω be the projections of l and a. 1 The angle between the planes they lie in satisfies ω < 15°, therefore |l|, |a1|, and |b1| satisfy the following relationship:

[0050] |a 1 |=|l|×cos(ω),

[0051] |b 1 | = |l| × cos(15 - ω).

[0052] Since ω < 15°, and cos(15) = 0.966, and the cosine function is monotonically decreasing within 0 to 90 degrees, therefore: 0.966 < cos(ω) ≤ 1, so we can obtain:

[0053] |a 1 | = |l| × cos(ω) ≈ |l|,

[0054] Therefore:

[0055]

[0056] To sum up, when the number of scanned pictures is 6, the difference between the maximum tilt angle and the actual tilt angle is < 4%, so we can use the maximum tilt angle to replace the actual tilt angle. And due to the relationship as shown in the appendix Figure 4 When finding the tilt direction of the plane where the maximum tilt angle is located, the tilt direction of the actual tilt angle must be within ±15° (the sign determination method is the same as before) of the maximum tilt angle direction. Therefore, we can use the midpoint degree of this interval to replace the tilt direction of the actual tilt angle, that is, the position where the tilt direction of the actual tilt angle is located is the maximum tilt angle direction ±7.5° (the sign determination method is the same as before). Therefore, we can obtain the following formula:

[0057] The actual tilt degree size ≈ the maximum tilt degree (the difference between the two is less than 1 - cos(90° / (the number of B - scanned pictures)))

[0058] The actual tilt degree direction ≈ the angle of the maximum tilt angle direction ± 45° / (the number of B - scanned pictures), and the plus or minus sign is determined by the position of the second - largest tilt angle (if the degree of the direction where the second - largest tilt angle is located is greater than the degree of the maximum tilt angle direction, it is positive, otherwise it is negative), and the difference between the estimated position and the actual position ≤ 45° / (the number of B - scanned pictures).

[0059] Example 4

[0060] Steps to measure the tilt degree of each group of lenses and intraocular lenses using a third - party software:

[0061] (1) As shown in the appendix Figure 1 Each group has 6 pictures in total.

[0062] (2) Export the measurement results to an EXCEL table, and the exported content is shown in Figure 8 .

[0063] (3) Determine the direction of the tilt angle based on the y-coordinates of the fitted circles of the front and rear parabolas. If the y-coordinate of the front surface parabola is greater than that of the rear surface parabola, the tilt angle is downward; otherwise, it is upward. Figure 5 and Figure 6 If the tilt angle is all downwards, then the tilt direction is 180 degrees.

[0064] (4) Use the same method to determine the tilt angle position in the 6 B scan images.

[0065] (5) Filter out the maximum and second largest tilt angles and the intervals containing them, including the first and second largest values. The interval containing the second largest value is the lower limit of the actual tilt angle interval, and the upper limit is 15 degrees above this. The actual tilt direction is (lower limit + upper limit) / 2. The maximum tilt angle ≈ the actual tilt angle. See [link to relevant documentation]. Figure 9 .

[0066] (6) The above are the steps for measuring the tilt angle by instruments that cannot directly obtain the tilt angle. Some instruments can directly output the size of the tilt angle and determine the positive or negative sign. After the data is output by such instruments, it goes directly to step (5).

Claims

1. A method for estimating the tilt angle of an actual lens and an artificial lens, characterized in that, Includes the following steps: S1: The tilt angle of the lens or intraocular lens in each B-scan image of each test subject is output by the measuring instrument, or if the instrument cannot directly output the tilt angle, the tilt angle is obtained by exporting each B-scan image and using image processing software to measure it using the three-point circle method. S2: Find the maximum and second maximum tilt angle of the test object; S3: Determine the direction of each tilt angle based on the angle of the maximum and second largest tilt angles; S4: The actual tilt angle is replaced by the maximum tilt angle. The actual tilt direction is located within the first interval, and the first interval is: [the location of the maximum tilt angle - 90° / (number of B-scan images), the location of the maximum tilt angle + 90° / (number of B-scan images)]; the location of the actual tilt angle is the midpoint of the first interval, that is, [the angle of the direction of the maximum tilt angle - 45° / (number of B-scan images), the angle of the direction of the maximum tilt angle + 45° / (number of B-scan images)].

2. The method for estimating the three-dimensional tilt of an actual lens and an artificial lens according to claim 1, characterized in that, In S4, the sign is determined by the position of the second largest tilt angle. It is positive when the degree of the direction of the second largest tilt angle is greater than the degree of the direction of the largest tilt angle, and negative otherwise.

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